Liquid-liquid extraction

Liquid-liquid extraction, also called solvent (solvent) extraction, is a selective separation process based on the different solubility of a substance in two insoluble phases (for example, petrol/water). An aqueous phase usually makes up one of the two phases.

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Liquid-liquid extraction is particularly suitable for processing large quantities. Flow rates of 100 m³/h and more can be easily archived with reasonable equipment dimensions. Energy consumption is usually negligible since the actual extraction process consumes small amount of energy. However, the subsequent regeneration stage - usually rectification - requires a corresponding expenditure of energy for the recovery of the extractant. For this purpose, the resulting raffinate phase must often be fed to a post-treatment. In general, the regeneration part of an extraction system requires energetic and investment costs many time that of the extraction. Accordingly, selection of the suitable extractant depends not only on the extraction selectivity, but also on the simplest and energetically most economical regeneration option.

Advantages

  • Very high flow rate possible
  • More energy-efficient process than direct distillation (example: separation of small amounts of substances with higher boiling from waste water)
  • Selective separation (where other processes - such as rectification - fail or are too time-consuming)
  • Gentle processing of heat-sensitive substances (for example, vitamins)

Stirred extraction columns

The stirred extraction column is like no other apparatus type universally applicable to virtually all liquid-liquid extractions. Only limiting conditions: Minimal density difference of 0.05 kg/m3 and low tendency for emulsion formation.

  • Flexible adaptation of the column geometry to the material and operational process conditions
  • Optimum drop size with variable stirrer speed defined adjustable
  • Insensitive to solids content
  • Mechanically simple design, low stirrer speed

Extraction column AMES 900-20